She is selective about things she can do. She would go to the table to eat or go to the toilet, but refuses to change her diaper in the morning even though she can. At almost all times, she tries to manipulate her family to do everything for her and not do anything at all. For months every day she acts as if she does not understand what she has to do. I get her to exercise by forcing her to do things for herself, but she is very persistent in not doing it and drives me crazy.
Perhaps backing off a little would be useful if she is manipulative (let her feel more control) and also is she has dementia.
You are right in that she needs some exercise, and activities of daily living can provide some of that. If she's manipulating, you may do accomplish more by backing off and not pushing. Once she feels she is in charge of what she does, it's possible she may do more. It's worth a try.
Take care of yourself, too. This is tough on the caregiver,
Carol